An asteroid is coined a Near
Earth Asteroid (NEA) when its trajectory brings it within 1.3 AU from the Sun.
A NEA is said to be a Potentially Hazardous Asteroid (PHA) when its orbit comes
to within 0.05 AU (= 19.5 LD = 7.5 million km) of the Earth's orbit and has a
measured absolute magnitude H < 22 mag (i.e., an estimated diameter D > 140 m).

As of 1 October 2017, 16722 NEAs
are known, including 7831 NEAs with D > 140, and 882 NEAs with D > 1 km (estimated population: 966 ± 50). Of these large NEAs, 157 are PHAs.

By listing in chronological order this broad selection of
milestones of NEA research, a global impression is offered of what has been
done and has happened, and what is being done and will happen in those fields,
as far as presently known.

By 1 October 2017, the NEA Chronology lists 3385
entries of known past events registered since AD 1800, including 376
close approaches of NEAs ranging in size from 1 to 325 m with nominal Earth
close approach distances d ≤ 1.00 LD (about 30 NEAs per year in recent
years; 53 in 2016; to date 33 in 2017), 22 of which with d ≤ 0.10 LD. Moreover,
there where four recorded impacts, in 1908, 2008, 2013, and 2014.

By 1 October 2017, the NEA Chronology lists 265
entries of known future events predicted up to AD 2200, of which 159 predicted
close approaches of NEAs with nominal Earth close approach distances d ≤
10.00 LD and minimum close approach distances d ≤ 1.00 LD (i.e., about
one per year), including 35 predicted close approaches of NEAs with nominal
Earth close approach distances d ≤ 1.00 LD, three of which with d ≤ 0.10 LD.

First and largest asteroid
discovered, 1 Ceres (H = 3.34 mag, D = 975 km, main-belt
asteroid), by Giuseppe Piazzi (1746 – 1826, Italy) at the Osservatorio
Astronomico di Palermo. Asteroid Cerere
Ferdinandea was
named in honour of King Ferdinand IV of Sicily, and later became known simply
as Ceres. Carl Gauss developed the math
to determine an accurate orbit for Ceres and published his results in November 1801. Given the definition of planets
and dwarfplanets accepted by the IAU XXVI General Assembly in 2006, Ceres is considered a dwarf planet rather than
an asteroid.

Weston Meteorite. At 6:30 hr on the morning of 14 December 1807, a
blazing fireball about two-thirds the size of the Moon was seen traveling
southwards by early risers in Vermont and Massachusetts (USA). Three loud
explosions were heard over the town of Weston in Fairfield County,
Connecticut. Stone fragments fell in at least 6 places.

- A. Ben-Menahem, September
1975, Physics of the Earth and Planetary Interiors, 11, 1,
"Source parameters of the Siberian
explosion of June 30, 1908, from analysis and synthesis of seismic
signals at four stations."

The Nakhla Meteorite fell to Earth on 28 June 1911 in the
Nakhla region of Abu Hommos (Alexandria, Egypt). Many people witnessed its
explosion in the upper atmosphere before the meteorite fell to Earth in an
area of 4.5 km in diameter. About forty pieces were recovered. Recovered
fragments ranged in weight from 20 to 1813 g.

Discovered by Johann Palisa
(1848 – 1925), discoverer of 122 asteroids at the Vienna Observatory
(Austria). Lost (the last missing), but rediscovered 1 May 2000 by Jeffrey A.
Larsen with the Spacewatch Telescope in Arizona (USA).

Ellemeet
Meteorite. Whit aloud noise, so that horses and cows took fright,
this meteorite fell down in a meadow near Ellemeet, on the island of Schouwen
(the Netherlands) on 28 August 1925, about 11:30 hr a.m.

- W.
Nieuwenkamp, 1927, Proc. Koninklijke Nederlandse Academie van
Wetenschappen, 1927, 724, "The Meteorite
of Ellemeet (after that of Uden in 1840, and that of Blauwkapel in
1843, the third known in the Netherlands)."

In December 1932, scientists
surveying the southern Egyptian desert came upon pieces of a translucent,
pale yellow-green, glassy substance, from tiny fragments to football-sized
chunks, scattered over a huge area at the Libyan border. Known as Libyan desert glass, this almost pure silica
contained isotopes showing it to be of extraterrestrial origin. Further
reading: see 3 March 2006.

Discovered by Karl W. Reinmuth
(1892 – 1979) at the Landessternwarte Heidelberg-Königstuhl (Heidelberg,
Germany); lost; recovered 15 October 2003. Arecibo radar observations on the
same day revealed it to be a binary asteroid, with components of D ≈
400 m, separated by 1200 m.

Chicora
meteoroid. A meteoroid exploded
as it entered the atmosphere above Chicora (PA, USA) on June 24, 1938. Based
on the size of the explosion, the rock's initial mass (before it broke up) may
have been more than 450 tons. However, only scant pieces of the meteorite
were ever found – located miles away from where the main mass, missing to
this day, is thought to have landed. Several reports on the Chicora meteorite mention that an unsuspecting
cow was struck and injured by one falling shard; other accounts say that the
poor animal was killed.

Daytime
Fireballover Bulannyo (Rhodesia). Norman Appleton witnessed a
meteor so bright he remembered it his entire life. Right before his eyes a
tremendous smoking fireball streaked across the daytime sky. Years later, as
an accomplished member of the Guild of Aviation Artists, he recorded his
memories in a painting.

IAU
Minor Planet Center (MPC),establishedby the International
Astronomical Union, Commission 20, and
succeeding the work which was carried out since 1910 by the Rechen-Institut in
Berlin-Dahlem (Germany), started operations at the Observatory of the
University of Cincinnati (Ohio, USA), director Paul Herget (1908 – 1981,
USA). At the time, 1564 minor planets were numbered. Upon Herget's retirement
in 1978, the amount of numbered minor planets had reached 2060, and the MPC moved to the Harvard-Smithsonian Center for
Astrophysics, Cambridge (MA, USA) with Brian G. Marsden (1937 – 2010) as
director. For a history of the MPC,
see:

Sikhote-Alin
Fireball and Airburst passed over
Sikhote-Alin mountains (Primorye, Russia), creating a 32 km long smoke trail
in the sky at an altitude of 5.6 km. The bright flash
and the deafening sound of the fall were observed at 300 km around the point
of impact, not far from Luchegorsk and ~
440 km northeast of Vladivostok. The pre-impact mass of the meteoroid may have been
100,000 kg. The strewn field of this meteorite covered an elliptical area of
about 1.3 km. Some fragments made craters, the largest of which was about 26
m across and 6 m deep.

The
international yearbook "Ephemerides of minor
planets", published since 1948 for the International Astronomical Union by the Institute of Applied Astronomy, St Petersburg (Russian Federation), contains information on orbital elements of numbered
minor planets and the circumstances of their observations during the best
observation periods.

Hodges meteorite. First
known modern case of a human hit by a space rock occurred
in Sylacauga (Alabama, USA). A 4 kg stone chondrite crashed through a roof
and hit Mrs. Ann Hodges in her living room after it bounced off her radio.
She was badly bruised. The Hodges meteorite,
or Sylacauga meteorite, is on exhibit
at the Alabama Museum of Natural History.

M.W. De Laubenfels (1956)
suggested the idea that the dinosaurs demise is due to an impact event and
the resulting super-hot winds that would result. He scaled up the effects of
the Tunguska blast and made first
suggestion of the death of the dinosaurs being impact related. Mammals first
appeared in Cretaceous with the most outstanding type differing little from
the modern opossum. The author argues for a brief period of extreme heat
enough to kill exposed large animals. Birds, mammals, aquatic animals would
have survived. He notes in October 1937 the close Earth approach of Hermesand the
Tunguska event. He computes an amount
of heat available from a 100 m sized impactor at 10 km/s and notes that if
kinetic energy turned into heat, it would be enough to boil 1016 tons of water whereas entire oceans are 1018 tons.

E.J. Öpik, 1958, Irish
Astronomical Journal,5, 34, "On the catastrophic effect of
collisions with celestial bodies." Öpik proposed that NEO impacts might
have handicapped the development of land in the paleontological history.

Příbram Meteorite Fall, the first meteorite simultaneously
observed by several stations in the Czech Republic. The network was initiated
locally at Ondřejov
Observatory. By 1963, the network consisted of 5 stations.
In 1968 it had expanded by the installation of about 15 new stations in
Germany, and was named the European Fireball
Network.

Eugene M. Shoemaker and
Edward C.T. Chao proved that Nördlingen
Ries crater(d = 24 km, Nördlingen,
western Bavaria, Germany), formed ~14.4 My ago in the Miocene, was caused by
meteorite impact. Another impact crater, the much smaller
(3.8 km diameter) Steinheim crater,
is located ~ 42 km WSW from the centre of Ries. The two craters are believed
to have formed nearly simultaneously by the impact of a binary
asteroid. The impactors probably had diameters of ~
1.5 km (Ries) and 150 m (Steinheim), and a pre-impact separation of
some tens of kilometers.

Eugene M. Shoemaker (1928 – 1997, USA) and colleagues firmly established the impact origin of the
Meteor Crater in Arizona. Meteor Crater is located approximately 69 km east of Flagstaff,
near Winslow in the northern Arizona desert of the United States. The
site was formerly known as the Canyon Diablo Crater. Scientists generally
refer to it as Barringer Crater, in
honor of the geologist Daniel Barringer (1860 – 1929) who was first to
suggest that it was produced by meteorite impact. Barringer
Meteor Crater lies at an elevation of about 1,740 m above sea
level. It is ~ 1,200 m in diameter, 170 m deep, and is surrounded by a rim
that rises 45 m above the surrounding plains. The center of the crater
is filled with 210 – 240 m of rubble lying above crater bedrock. The incoming
asteroid had a diameter of ~ 25 m and a velocity of 15 km/s. The largest
meteorite found is the so-called Holsinger meteorite, weighing 639 kg, on
display in the Meteor Crater Visitor Center on the rim of the crater.

In an UPI report, Australian
scientist S.T. Butler noted an upcoming close Earth approach by the asteroid 1566Icarus(1949 MA, H =
16.0 mag, D = 1.3 km, PHA)in 1968. He
suggested that the asteroid could possibly be destroyed by a nuclear warhead
if it neared the Earth. Paul Sandorff (MIT, U.S.A.) then assigned a
hypothetical problem to his system engineering class. This “Icarus Project” drew a good deal of attention,
including a Time Magazine story in June 1967 and a book the following
year.

The
largest know meteorite, the Hoba
meteorite, lies on the farm "Hoba
West", not far from Grootfontein, in the Otjozondjupa Region of Namibia.
It has been uncovered in 1920, but, because of its large mass, has never been
moved from where it fell. The main mass is estimated at 54,000 kg, and it is
the largest known meteorite (as a single piece) and the most massive
naturally-occurring piece of iron known at the Earth's surface. The Hoba meteorite is
thought to have landed less than 80,000 years ago. It is inferred that the
Earth's atmosphere slowed the object down to the point that it fell to the
surface at terminal velocity, thereby remaining intact and causing little
excavation. The Hoba meteorite is unusual in that it is flat on both major surfaces,
possibly causing it to have skipped across the top of the atmosphere in the
way a flat stone skips on water. Size: 2.7 × 2.7 × 0.9 m.

Chihuahua
Fireball, witnessed falling over the
Mexican State of Chihuahua. After breaking up in the
atmosphere, an extensive search for pieces was conducted; it is often
described as "the best-studied meteorite in history." Some 2000 kg
of meteorite material has been collected. The largest piece found, the Allende meteorite of 0.520 kg, is notable for
possessing abundant, large calcium-aluminum-rich inclusions, which are among
the oldest objects formed in the Solar System. The 238U/235U
isotope ratio found in the Allende meteorite by Brennecka et al. (2010) implies that the Solar System is some 5 million
years younger than thought previously.

MurchisonFireball and Meteorite. Near the town of Murchison
(Victoria, Australia),
a bright fireball was
observed to separate into three fragments before disappearing, leaving a
cloud of smoke. About 30 seconds later, a tremor was heard. Many specimens
were found over an area larger than 13 km², with individual masses up to 7
kg; one piece, weighing 680 g, broke through a roof. The total collected mass
exceeds 100 kg.

The Japanese Antarctic
Research Expedition discovered nine meteorites on the blue ice
field of the Yamato Mountains in Antarctica, December 1969. This was the
first significant recovery of Antarctic meteorites and represented samples of
several different types. In 2011, co-researchers from the USA, South Korea
and Japan have found in meteorite Yamato 691a new mineral, dubbed "Wassonite",
formed from sulfur and titanium, and possessing a unique crystal structure
that has not been previously observed in nature.

Lost
City Fireball. Four stations (Hominy OK, Woodward OK, Pleasanton KS,
and Garden City KS) of the Prairie
Meteorite Network simultaneously
photographed the track of a meteoroid fireball. Analysis of the photographs
indicated that a meteorite might have landed within an area east of Lost City
(OK, USA). This was the first time in the US that simultaneous photography of
a fireball from multiple observation points was achieved, making it possible
to calculate a trajectory and delimit a search area on the ground. Six days
later, a 9.83 kg (21.6 pound) meteorite was spotted sitting in a snow-covered
dirt road within one-half mile of Lost City. Three additional smaller
meteorite fragments were recovered later (272 g, 640 g, 6.6 kg).

Ref:

- Z.
Ceplecha, 1996, Astronomy & Astrophysics, 311, 329, "Luminous
efficiency based on photographic observations of the Lost City fireball and implications for the influx of interplanetary bodies onto Earth."

Great
Daylight 1972 Fireball(US19720810), Earth-grazing asteroid, estimated D ≈
3-14 m, 100-sec passage with 15 km/s through the Earth atmosphere, 57 km high
over the Rocky Mountains from Utah (USA) to Alberta (Canada). Co-inciding
with the annual Perseid meteor
shower. Suggestions that this object is still in an Earth crossing orbit
around the Sun and passed close to the Earth again in August 1997 have not
been substantiated (Spahr, 2010, private communication).

A. Ben-Menahem, 1975, Physics
of the Earth and Planetary Interiors, 11, 1, "Source parameters of
the Siberian explosion of June 30, 1908,
from analysis and synthesis of seismic signals at four stations."

Jilin
MeteoriteShower, near Jilin City
(Jilin Province, China), had a dispersion ellipse of 72 × 8.5 km and landed
over 100 fragments with a total mass > 2700 kg. The largest of these
fragments weighs 1770 kg and presents the largest stony meteorite known.

IAU
Minor Planet Center moved to Smithsonian Astrophysical
Observatory, Cambridge (MA, USA). Brian G. Marsden, director. Up to this
time, the set of numbered minor planets had increased to 2060, with nearly
180,000 observations in the archive.

Spacewatch program started by Tom Gehrels and Robert S. McMillan, LPL,
UA, Tucson (AZ, USA). Routine detections started in 1984, survey
started in 1989. CCD-scanning observations are conducted 20 nights each
lunation with the Steward Observatory 0.9-m Spacewatch
Telescope (down to v = 21 mag) and the Spacewatch 1.8-m telescope (down to v =
23 mag), both on Kitt Peak (AZ, USA). From 1992 to 1995Spacewatch automatically detected more than
60,000 asteroids down to v = 21 mag.

Nobel Prize winning physicist
Luiz W. Alvarez (1911 – 1988, USA) and colleagues published their seminal
paper (1980), associating the
extinction of dinosaurs ~65.5 Myr ago with the direct impact of a large
asteroid or comet. Ten years later after this initial proposal, evidence of a
huge impact crater called Chicxulub,
off the coast of Yucatán Peninsula (Mexico), strongly confirmed their theory.
The crater center is located near the town Chicxulub. The crater diameter is
over 180 km, maybe even 300 km, making the feature one of the largest
confirmed impact craters on Earth. The crater was discovered by the
geophysicist Glen Penfield, who had been looking for oil in Yucatán during
the late-1970s. Returning later he found evidence for the impact theory (A.R.
Hildebrand et al., 1991). The impacting NEO that formed the crater had a
diameter D = 10 ± 4 km; the explosion released an energy of about 5 ×
107 megaton TNT, substantially more powerful than the largest
known volcanic eruption. W.F. Bottke et al. (2007) suggested that the
impacting NEO was a member of the Baptistina
family of asteroids, created by a collision of two main-belt
asteroids (with D = 170 km and 60 km) 160 Myr ago, the largest
surviving orbiting member of which is main-belt asteroid 298 Baptistina(D = 13-30 km), discovered in 1890 by Auguste H.
Charlois (1864 – 1910) at the
Observatoire de Nice (France). But see Masiero et al. (2011). Schulte et al.
(2010) summarized evidence that the Chicxulub impact triggered the
mass extinction ~65.5 year ago.

- J. Vellekoop, A. Sluijs, J. Smit, et
al., 12 May 2014, Proceedings of the National Academy of Sciences,
published ahead of print, "Rapid short-term cooling following the Chicxulub impact at the Cretaceous–Paleogene
boundary."

Fred L. Whipple (1906 – 2004,
USA): “Protection of the Earth from undesirable impacting bodies is not
just a science fiction project for some improbable future. The cost might be
comparable to, even smaller than, the world’s current military expenditures.
We could choose to do it now. We could choose to protect ourselves from
asteroids and comets rather than from each other.” Ref: F.L. Whipple,
1985, The Mystery of Comets (Baltimore: Smithsonian Institution
Press).

Re-discovery of the largest
known PHA: 4179 Toutatis, 1989 AC(H = 15.3 mag, D = 4.6×2.4×1.9 km, P = 4.03 yr). It
was first sighted on February 10, 1934, as object 1934
CT, and then promptly lost. Re-discovery on January 4, 1989, by
Christian Pollas (France), and was named after the Celtic god
Toutatis/Teutates, known to popular culture as the God the cartoon character
Astérix's chief Vitalstatistix evokes so that the sky may never fall on his head. Radar imagery has shown

that Toutatis is a irregular body consisting of two distinct "lobes", with
maximum widths of about 4.6 km and 2.4 km respectively. It is hypothesized
that Toutatis formed from two originally separate bodies which coalesced at some
point, with the resultant asteroid being compared to a "rubble pile".

From 1990 until its
termination in 1996, Duncan Steel, director of Spaceguard Australia and Vice-President of The Spaceguard Foundation(see 26 March
1996), directed the southern hemisphere program Anglo-Australian Near Earth Asteroid Survey (AANEAS) for the discovery and tracking of near-Earth
asteroids, based at the Anglo-Australian Observatory, using the UK 1.2m
Schmidt Telescope.

Glanerbrug
meteorite. A fireball seen
by hundreds of people in the Netherlands, Germany and Denmark resulted in an
impact of an 885 g meteorite, riddling the roof of a home in Glanerbrug (the
Netherlands).

US Congress House in NASA
Multiyear Authorization Act of 1990: "imperative that detection rate of
Earth-orbit-crossing asteroids must be increased substantially, and that
means to destroy or alter orbits … should be defined and agreed
internationally."

US Congresssional Statement
1991: "The House Committee on Science and Technology believes that it is
imperative that the detection rate of Earth‐orbit‐crossing asteroids must be
increased substantially, and that the means to destroy or alter the orbits of
asteroids when they do threaten collisions should be defined and agreed upon
internationally. The chances of the Earth being struck by a large asteroid
are extremely small, but because the consequences of such a collision are
extremely large, the Committee believes it is only prudent to assess the
nature of the threat and prepare to deal with it." NASA Authorization
Bill, 1991.

The US Congress House Committee
on Science and Technology used NASA Authorization Bill to direct NASA to
study (1) a programme to increase detection rate of Earth-orbit-crossing
asteroids addressing costs, schedule, technology and equipment (Spaceguard Survey Report); (2) systems and
technologies to destroy or alter orbits of such asteroids if they should pose
a danger to life on Earth (NEO Interception
Workshop).

IAU
XXI General Assembly, Buenos Aires (Argentina). Resolution by IAU
Commission 20 on Positions and Motions of Asteroids, Comets and Satellites,
under the presidency of Richard West, calling for an IAU Inter-Commission Working Group on Near Earth
Objects (WG-NEO).

The Spaceguard Survey: Report
of the NASA International NEO Detection Workshop, D. Morrison (ed.), 1992 (Washington DC: NASA).Delivered to US Congress. Recommends a search programme and international collaboration to find objects
with D > 1 km; and the provision of six ground based telescopes,
northern and southern hemisphere sites, southern hemisphere radar; half costs
to come from international partners.

The term Spaceguard loosely refers to a number of
efforts to discover and study NEOs. The British author Arthur C. Clarke (1917
– 2008) coined the name in his novel Rendezvous with Rama (London:
Victor Gollancz, 1973) where Spaceguardwas the name of an early warning system. The name
was later adopted by a number of real life efforts to discover and study
NEOs. The IAU Working Group on Near-Earth Objects
(WG-NEO) presented a paper in September 1995 entitled Beginning the Spaceguard Survey, which led
on 26 March 1996 to the international organization called the SpaceguardFoundation
(SGF).

Peekskill
Fireball and Meteorite. Afireball was seen streaking
across the sky from Kentucky to New York. At least
14 people captured part of the fireball on videotape. A 12-kilogram stony
meteorite (chondrite) from the fireball fell in Peekskill (NY, USA), smashed
the trunk of a parked automobile and came to rest beneath it.

NASA
Planetary Astronomy Program Office begins ramp up of funding for
NEO observations.

1993

Major L.N. Johnson, 1993,
White Paper, presented to SPACECAST 2020,
"Preparing for Planetary Defense:
detection and interception of asteroids on collision course with Earth."
In this paper the term Planetary Defense was coined.

European Science Foundation
(ESF) initiates new scientific network "Impact
Cratering and Evolution of Planet Earth." This led to the
submission of a Research Networking Programme proposal in 1998,
"Response of the Earth System to Impact Processes (IMPACT)",
approved for five years, 1998 to 2002. Four workshops were held in 2002 –
2003."

T. Gehrels, M.S. Matthews
& A.M. Schumann (eds.), 1994, Hazards Due to Comets and Asteroids (Tucson: Univ. of Arizona Press). Proceedings of four Workshops in April/May
1991, January 1992, January 1993, and May 1993.

US Congress House Committee on
Science and Technology passed an amendment to NASA Authorization Bill
directing NASA to report within a year with a programme to identify and
catalogue, with help from the Department of Defense and space agencies of
other countries, within 10 year, orbital characteristics of all comets and
asteroids with D > 1 km and in an orbit that crosses Earth’s.

Marshall
Islands Fireball and Airbursts. A large meteoroid impacted over the Pacific Ocean at
2.6° N, 164.1° E, 300 km south of Kosrae (Micronesia).
The impact was observed by space-based infrared sensors operated by the U.S.
Department of Defense and by visible wavelength sensors operated by the U.S.
Department of Energy. During entry the object broke into several pieces, one
of which detonated at 34 km and another at 21 km altitude. M ≈ 1.6×105 kg - 4.4×106 kg; D ≈ 4.4
- 13.5 m.

St-Robert
Daylight Fireball and Meteorite Fall over the Canada-US border,
travelling at a velocity of ~13 km/s, widely seen from the provinces of
Quebec and Ontario and the states of New Hampshire, Vermont and New York at
distances up to ~500 km. The rock fragmented spectacularly ~50 km NE of
Montreal at an altitude of ~36 km; hundreds of fragments have been found
with pieces of up to 6.5 kg.

IAU
XXII General Assembly, Den Haag (the Netherlands). The IAU Working Group on Near Earth Objects, chaired by Andrea Carusi, had a science meeting,
and presented a report recommending that an international authority should
take responsibility for NEO investigations and initiatives.

The (1.0/1.2m) Schmidt CCD Asteroid Program (SCAP) of the
Beijing Astronomical Observatory put in practice, a NEO search telescope in
operation at the Xuyu Station of the Purple Mountain Observatory, 120 km
north of Nanjing (China).

Planetary
Defense Workshop: An International Technical Meeting on Active Defense of the
Terrestrial Biosphere from Impacts by Large Asteroids and Comets,
Livermore (CA, USA). Proceedings: LLNL CONF-9505266. Report by Peter Tyson.

IAU
Working Group on Near Earth Objects Workshop, Vulcano (Italy),
Beginning the Spaceguard Survey.TheWorkshop participants agreed to set up a Spaceguard Foundation,
which materialized on 26 September 1996, in Rome. The Spaceguard Central Node (SCN), hosted by ESA at ESRIN (Frascati, Italy) is a web site
of The Spaceguard Foundation. Since 2002, the SCN is supporting ESA’s
Science Programme in all issues related to NEOs.

Near Earth Asteroid Tracking (NEAT) program run by NASA and JPL to discover NEOs, from December 1995 to
April 2007. The project employed two telescopes, on Maui (1m GEODSS telescope, HI, USA) and Mt. Palomar (1.2m
Schmidt, CA, USA). Ref:

Fifth United Nations/European Space Agency Workshop on Basic
Space Science: From Small Telescopes to Space Missions, hosted by the Arthur C. Clarke Center for
Modern Technology on behalf of the Government of Sri Lanka, Colombo, Sri
Lanka. Report (A/AC.105/640, 14 May 1996) resolves that an international
network of telescopes under UN aegis is needed for NEO searching and
tracking.

Presentation by Adriane C. Ocampo at the 27th Annual Lunar and Planetary Science
Conference, 18 – 22 March
1996 in Houston (TX, USA) on a chain of impact craters in Chad suggested by
space-borne radar images, possibly caused by a large, fragmented comet
or asteroid similar to the Shoemaker-Levy 9 comet that slammed into Jupiter in 1994. The craters were discovered in radar
images of the Earth taken by the Spaceborne Imaging Radar C/X-band Synthetic
Aperture Radar (SIR-C/X-SAR) that flew on the Space
ShuttleEndeavour in April and October of 1994.

Parliamentary Assembly of the
Council of Europe (Strasbourg, France), Resolution 1080: "On the
detection of asteroids and comets potentially dangerous to mankind",
invited governments of member states and the European Space Agency (ESA) to
give the necessary support to an international program to detect NEOs that
are potentially dangerous to mankind and to develop a strategy for remedies
against possible impacts.

Inauguration of the Spaceguard Foundation (SGF), Rome (Italy),
founded by E. Shoemaker, D. Steel, A. Carusi and the IAU WG-NEO. The SGF
is located at the ESA Centre for Earth Observations (ESRIN) in
Frascati (Italy).

Start of the OCA-DLR Asteroid Survey (O.D.A.S.), to search
for asteroids and comets with emphasis on NEO's, operated from October 1996
to April 1999 by the Observatoire de Côte d'Azur (OCA, Nice, France) and the
DLR – Institute of Planetary Research (Berlin-Adlershof, Germany), in the
framework of the EUNEASO project. Five
NEAs were discovered.

The Japanese Spaceguard Association (JSGA) officially founded.
Plans for the future involved two 1-m class ground-based NEO telescopes in
Japan and a 30-cm NEO telescope on the Moon. A 1-m wide-field telescope for
NEO detection became operational in 2002, and observes NEOs down to v = 20.5 since 2006.

The
survey projectLincoln NEA Research (LINEAR), a MIT Lincoln Laboratory program funded by the US
Air Force and NASA, began operations with robotic telescopes and fast
read-out CCD. Two LINEAR 1-m
telescopes (White Sands Missile Range, Socorro, NM, USA) observe the sky five
times per night. A third telescope is used for confirmation of NEO orbits,
down to v = 20 mag. As of 31 December 2007, LINEAR had detected 2019 NEAs and 236 comets.

El
Paso superbolide. A large fireball seen at
daylight from Chihuahua (Mexico) moving north to detonate east of El Paso
(TX, USA). Recorded by satellite systems, seismographs, infrasound
arrays and numerous video and still photographers. The terminal disaggregation
energy released corresponds to a body of ~2 m and total mass of M ≈
15,000 kg.

US Department of Defense Clementine II mission to test
technologies for interception of asteroids has fallen victim to a line-item
veto: US President Clinton deleted $30M in funding for Clementine II from the FY1998 budget. Clementine II was
supposed to fly by asteroids 4179
Toutatis and 1986 JK in the year
2000 and possibly to deliver impact probes.

First
asteroid discovered byLowell Observatory
NEO Search (LONEOS), initiated by E.L.G. Bowell. The 0.6m
telescope project, funded by NASA, was terminated at the end of February
2008. LONEOS discovered 288 NEOs.

The Catalina Sky Survey came into operation,
starting from the ashes of an old photographic project started by Spahr &
Hergenrother (1993). The CSS consists
of a consortium of three cooperating surveys, all funded by NASA: the
original Catalina Sky Survey (CSS, 0.7-m telescope) in Arizona, the Siding Spring
Survey (SSS, 0.5-m telescope) in Australia, and the Mt. Lemmon
Survey (MLSS,
1.5-m telescope) in Arizona. As of 2009, CSS had discovered more than 2,142 NEOs down to v = 22 mag.

U.S.
Congressional Hearing on NEOs and Planetary Defense. Statement
by Carl Pilcher, Science Director, Solar System Exploration, Office of Space
Science, NASA, announcing the SpaceguardGoal to
the U.S. House Subcommittee on Space & Aeronautics, i.e., find and track
90% of NEOs with D > 1 km.

The International Astronomical Union Executive Committee, at its
71st meeting in Paris, on the initiative of General Secretary
Johannes Andersen, issued a policy statement, which made clear that the
detection and observations of NEOs to determine their orbits "is an
international responsibility that requires the efforts of and support for
astronomers around the world." It also stated that the IAU "coordinates
this activity through the IAU Working Group on
Near Earth Objects (WG-NEO) and offers the services of the Minor Planet Center, the international clearing house and data disseminator
for NEO observations and research." It was emphasized that this
was not a scientific policy judgment, but a policy issue related to public
safety.

The threat from NEOs is
debated in the UK House of Commons. Minister for Energy & Industry, John
Battle, said that the government will consult British astronomers and other
experts on ways the UK can support NEO research.

1999, Mar 5-6

Near Earth Objects Dynamic
Site (NEODyS) created, as an Italian/Spanish service that provides
information on NEOs, operated at the University of Pisa (Italy), with a
mirror site in Valladolid (Spain). Operational since November 1999. Both the
University of Pisa and JPL post their web sites for information on NEOs
(close approaches, ephemerides, orbital data). The close approach monitoring
efforts, CLOMON at Pisa and SENTRY at NASA-JPL were initiated later. Since
early 2002 the two automated NEO close approach monitoring services, CLOMON2 (Pisa) and SENTRY (JPL), are cross-checking their monitoring results. Starting
from 1 September 2011 NEODyS is sponsored by ESA, which pays a portion of the
operating costs, both for the background orbit and risk computations and for
the database and web interface; the rest of the cost is covered, as before,
by the Department of Mathematics, University of Pisa, with the running
research grants of the Celestial Mechanics Group, and by IASF-INAF (Rome),
with a PRIN-INAF grant.

NASA/USAF
NEO Search Program. NASA, in collaboration with the USA Air Force,
is moving to implement a search program to meet the objectives of the Spaceguard Survey, as set down in the NASA Spaceguard reports of 1992 and 1995.

In a report to the ESA Council
at ministerial level, the ESA Long-Term Space Policy Committee recommended
(Action 13, Threat of Cosmic Collision) that ESA be involved in NEO
activities, including the study of counter measures. Ref: LSPC Report
"Investing in Space – the Challenge for Europe", 1999, ESA SP-2000.